As hybrid powertrains that include an energy storage device as part of an energy storage system (ESS), gain favor over conventional powertrains or hybrid powertrains that do not include such a device, energy management systems are being developed that will maximize overall fuel efficiency and prolong the life of said energy storage devices. Such devices may include batteries, supercapacitors, or other suitable devices, with the battery being the main device referred to herein. Of particular importance presently is a management system that defines the functional requirements for a hybrid electric swing drive system with ESS to be used on a hydraulic excavator (HEX). Energy management systems incorporating ESS are particularly attractive in HEX settings because of the predictable, repeated operation cycles. That is, the HEX operates the majority of the time in a known repeated cycle having (1) a motoring period where a swing motor or other energy supply component initiates rotational movement of the HEX's bucket, stick/boom, optional load, cab, etc. and (2) a breaking period where force is exerted to slow and stop said rotational movement. When an ESS is incorporated, energy can be stored during the breaking period for use during, e.g., the motoring period. Moreover, the swing mechanism has high inertial forces that do not exist in most other work machines, making it a favorable setting in which to utilize ESS.
One approach of managing hybrid energy systems is disclosed in by Bouchon (U.S. Pat. No. 6,909,200). Bouchon discloses an energy management system where energy recovered from regenerative breaking is preferred over energy supplied by the energy generating device. However, Bouchon is silent regarding energy management of energy generated during a swing cycle of a hybrid HEX and, more importantly, is silent regarding limiting the energy taken from the battery.